This invention relates to a water seal packing for sealing water at the coupling portion of underwater structures such as tunnels or the like disposed under a sea or river.
In general, when tunnel is constructed under water, there has been employed a common process for excavating a rock layer under the sea bed, a shield process for excavating earth and sand for temporarily shutting off the waterway when constructing tunnel tubes. There has recently been developed, however, a process for placing tunnel tubes under the sea bed wherein tubes are connected to each other under water so as to constitute a tunnel.
In such a process for setting the tube, a serious problem takes place which relates to obtaining a device for positively sealing water out of the coupling portion of tunnel tubes even if the tunnel tubes tend to be separated from each other due to extension and contraction of the tunnel tubes.
U.S. Pat. No. 3,729,939 has proved effective for positively sealing water out at the coupling portion of tunnel tube, however, the device in said patent is not effective enough to allow movements of the tunnel tubes, i.e. the device can not follow a large displacement of the tunnel tubes.